Means for applying coatings to tablets or the like



. i. (Jigy 9 D. E. WURSTER 2,799,241

MEANS FOR APPLYING COATINGS TO TABLETS OR THE LIKE Original Filed Jan. 21, 1949 RECOVERY Am: I Ex www- ALONG WALL OF 10 A Cum-1m: CHAMBER 6 'llbfibhhdr Q 7 3 INLET Compnzssco 2 POWDERED AIR Lac-rose ACACIA SOLUTION o HEATmr: 5UGAR Emmanu- Soun-lon Ram CAOMPRESSEO OUTLET To POLISHING 22 PAN AIR

IN VEN TOR.

United States Patent MEANS FOR APPLYING COATINGS TO TABLETS OR THE LIKE Dale E. Wurster, Madison, Wis,

Alumni Research Foundation, Madison, ration of Wisconsin assignor to Wisconsin =Wis., a corpo- 21, 1949, Serial No. 71,977, dated August 11, 1953. Di-

Serial No.

8 Claims. (Cl. 118-24) My invention relates, generally, to methods of and means for applying coatings, and it has particular relation to the coating of medicinal tablets, chewing gum, candy, nuts, etc. This application is a division of application Serial No. 71,997, filed January 21, 1949, now Patent No. 2,648,609, issued August ll, 1953.

Among the objects of my invention are: To support the tablets in air in a coating chamber and to coat the same while they are so positioned; to support the tablets in an upwardly flowing air stream; to 'heat the air prior to its contact with the tablets to dry the coating thereon; to cause the air to flow in a turbulent fashion and tumble the tablets so that they may be coated uniformly; to move the tablets downwardly on a bias transversely of the air stream while they are being coated; to introduce the coating material into the air stream underneath its initial contact point with the tablets; to introduce individually into the air stream different coating materials; and to direct a current of air upwardly in the coating chamber along its inner surface to prevent the coating material from impinging .thereon.

Other objects of my invention will, and in part appear hereinafter.

This invention is disclosed in the embodiment thereof shown in the accompanying drawing and it comprises the features of construction, combination of elements and arrangement of parts which will be set forth in detail hereinafter and the scope of .the application of which will be indicated in the appended claims.

For a more complete understanding of the nature and scope of my invention, reference can be had to the following detailed description, taken together with the accompanying drawing, in which:

Figure 1 is a longitudinal-sectional view of a coating mechanism constructed ,in accordance with my invention;

Figure 2 is a view partly in section and partly in elevain part, be obvious 2,799,241 Patented July 16, 1957 tube 17 may discharge into a polishing pan .or similar receptacle. Slides 18 and 19 may be provided in the outlet tube 17 for controlling the flow of the coated tab lets therethrough in batches similar to the manner in which they are permitted to flow onto the screen 15 by the slides 13 and 14.

It is desirable that the uncoated and partially coated tablets above the screen 15 be supported in air so that they can be evenly coated. For this purpose air jets 20 and 21 are positioned in the lower end of the chamber 10 below the screen 15 and are directed upwardly to supply an air stream flowing upwardly in the chamber 10 of sufiicient velocity to maintain the uncoated and partially coated tablets slightly out of contact with the screen 15. The air jets 20 and 21 may be connected by conduits 20' and 21 to a suitable source of compressed air, the pressure of which is adjusted so as to maintain the 111117 coated and partially coated tablets slightly above the screen 15 to be coated in a manner to be described presently.

Not only is it desirable that the tablets be supported in the air stream which flows upwardly through the coating chamber 10 but also it is desirable that they be tumbled so as .to coat the same more uniformly. For this purpose the flow of air through the coating chamber 10 is arranged so that, in place of it being a streamlined flow, it is a turbulent flow. For this purpose a disc 22 is provided which may be rotated at ,a constantspeed by ,a motor 23. As shown more clearly in Figure 3 the .disc 22 has circular rows 24, 25, 26, and :27 of perforations through whichthe air from the jets 20 and 21 flows. As shown in Figure 1 the air jets 20 and 21 register with the circular rows 24, '25, '26 and 27 of perforations .so that the air from the former is directed by the row of perforations individual thereto. Also as shown in Figure '1 the rows 24 and 27 of the perforations are inclined-inwardly while the row 25 of perforations is inclined outwardly. The remaining row 26 extends vertically through the disc 22. The several air streams thus directed by the perforations 24, 25, 26, and 27 impinge on the uncoated and partially coated tablets above the screen 15 in a turbulent fashionand cause them-to be tumbled so thatthey tion at an enlarged scale showing in more detail the construction of the manifold which directs air upwardly along the inner surface of the coating chamber; and

Figure 3 is a top plan view of the rotating disc which causes the air to flow in a turbulent fashion.

Referring now particularly to'the drawing, it will be observed that the reference character 10 designates a vertically positioned coating chamber which may be formed of metal or glass. The coating chamber 10 preferably has a circular cross section, and it may be of conical, modified conical, or cylindrical shape as may be desired. Near its lower end there is provided an entrance 11 for the tablets to be coated. An inlet tube 12 communicates with the entrance 11 and slides 13 and 14 are positioned therein to permit the introduction of the tablets to be coated into the chamber 10 in batches.

Within the chamber 10 there is a screen 15 which extends transversely thereacross and on a bias so that the tablets to be coated, and while they are being coated, move across the chamber 10 and downwardly to an exit 16 with which an outlet tube 17 communicates. The

can be evenly and completely coated with the coating material.

With a view to dryingquickly the coating material on the tablets, provision is made for heating the air as it passes upwardly through the :chamber 10 underneath the screen 15. For this purpose an electric heater element 28,in the form of a grid, may be positioned immediately above the rotating disc 22. It will be understood that the heater element 28 may be connected for energization to a suitable current source and .that the degree of heat can be varied by varying the amount of current flowing therethrough.

mined'by the number of -.different.coating materials -to be employed. Each of itheconduits ;30, 31 and :32 terminates in a nozzle 33 which, as shown in Figure l, is directed against the tablets near the upper edge of the screen 15 so that the coating material is supplied to the tablets as soon as they pass through the entrance 11. It will be understood that various coating materials can be supplied. As illustrated in Figure 1, the conduit 30 is arranged to have powdered lactose blown therethrough. The conduit 31 carries an acacia solution, while the conduit 32 may carry a sugar solution. It will be understood that these particular materials are mentioned for illustrative purposes only and that other coating materials can be used as may be desired.

Certain of the coating materials may tend to adhere to the inner surface of the coating chamber particularly in the immediate vicinity of the screen 15. In order to prevent this a ring-like manifold 34 may be positioned just above the screen 15. As shown in Figure 2 the manifold 34 has outwardly and upwardly directed openings or apertures 35 which cause air supplied to the manifold 34 from a suitable source of compressed air to flow in the directions indicated by the arrows 36 over the inner surface of the chamber 10 for preventing the coating material from engaging the same.

At the upper end of the coating chamber 10 a screen 37 may be provided to prevent the escape of tablets in the event that the pressure supplied through the jets and 21 should be sufficiently great as to cause them to rise to this position. An exhaust tube 38 connects the coating chamber 10 to a suitable recovery and exhaust chamber as will be understood readily.

In operation, the motor 23 is energized to drive the disc 22 at the desired speed. Air under pressure is supplied through the conduits 20' and 21' to the jets 20 and 21 respectivelyso that the uncoated and partially coated tablets on the screen 15 will be tumbled thereabove. This air pressure also is adjusted so that when the tablets are fully coated it will be insufiicient to maintain them above the screen 15 at the lower end thereof adjacent the exit 16. The current flowing through the heating element 28 is adjusted so that the coating applied to the tablets above the screen 15 is dried satisfactorily. The coating materials supplied to the conduits 30, 31 and 32 are arranged and adjusted so that the desired proportions will be applied to the tablets at rates which will provide the desired thickness of coating. Air is supplied to the manifold 34, it being understood that the pressure at the apertures 35 therein is slightly greater than the air pressure at the air jets 20 and 21 so that the desired air flow takes place along the inner surface of the chamber 10 to prevent the coating material from impinging thereon.

Now, the slide 13 is raised to permit a charge of uncoated tablets to flow downwardly through the inlet tube 12 against the slide 14. The slide 13 is closed and then the slide 14 is opened. The uncoated tablets flow through the entrance 11 onto the upper end of the screen 15 and are immediately lifted thereabove and tumbled. At the same time they are subjected to the atomized flow of coating materials from the nozzles 33 which are supplied individually by the conduits 30, 31 and 32 in the manner described. The partially coated tablets move transversely of the chamber 10 and downwardly on a bias but are still being tumbled above the screen 15 until the coating thereon is sufliciently heavy so that the upwardly flowing air stream is insufiicient to maintain them out of contact with the screen 15. When all of the tablets have been completely coated, the slide 18 is opened and they are allowed to discharge through the exit 16 into the outlet tube 17. Thereafter the slide 18 is closed and the slide 19 is opened to permit the coated tablets to be discharged into the polishing pan or other receptacle as may be desired.

It will be obvious that certain changes can be made in the foregoing construction without departing from the spirit and scope of this invention. Accordingly, it is intended that all matter shown in the accompanying drawing and described hereinbefore shall be interpreted as illustrative and not in a limiting sense.

I claim as my invention:

1. Apparatus for coating tablets or the like comprising, in combination, a vertically disposed coating chamber, screen means extending transversely of said chamber at its lower end for receiving the tablets to be coated, means for directing an air stream through said chamber in a vertical direction to react against the under sides of the tablets and suspend them in the lower part of said chamber against the force of gravity above said screen, and conduit means extending into said chamber for introducing the coating material into the air stream below the suspended tablets.

2. The invention, as set forth in claim 1, wherein means are provided for heating the air stream prior to contact with the tablets to dry quickly the coating applied thereto.

3. The invention, as set forth in claim 2, wherein means are provided to cause the air stream to flow turbulently to tumble the tablets so that they are coated uniformly.

4. The invention, as set forth in claim 1, wherein the screen means is disposed on a bias in the coating chamber, an entrance for the uncoated tablets is provided through the wall of said chamber at the top of said screen means, and an exit for the coated tablets is provided through the wall of said chamber at the bottom of said screen means.

51 The invention, as set forth in claim 4, wherein the conduit means discharges the coating material into the air stream near the top of the screen means and the velocity of the air stream is such that the uncoated and partially coated tablets are tumbled while the fully coated tablets are too heavy to be tumbled and fall to the lower end of said screen means.

6. The invention, as set forth in claim 1, wherein the conduit means comprises a plurality of conduits each arranged to introduce a separate coating material into the air stream.

7. The invention, as set forth in claim 1, wherein means are provided for directing a flow of air upwardly along the inner surface of the coating chamber above the screen means to prevent the coating material from impinging on said surface.

8. The invention, as set forth in claim 7, wherein the pressure at which the air is directed upwardly along the inner surface of the housing is greater than the pressure at which the air stream is directed upwardly for the support of the tablets.

References Cited in the file of this patent UNITED STATES PATENTS 1,473,165 Steigmeyer Nov. 6, 1923 1,546,922 Faber July 21, 1925 1,854,100 Brito Apr. 12, 1932 2,114,377 Goss Apr. 19, 1938 2,227,465 Roche et al. Jan. 7, 1941 2,339,932 Kuhl Jan. 25, 1944 2,561,392 Marshall July 24, 1951 2,563,475 Mahoney Aug. 7, 1951 2,648,609 Wurster Aug. 11, 1953 

